Make nonnull assertions and binding patterns apparent declared type locations

src/compiler/checker.ts

@@ -4308,7 +4308,8 @@ namespace ts {
                     if (strictNullChecks && declaration.flags & NodeFlags.Ambient && isParameterDeclaration(declaration)) {
                         parentType = getNonNullableType(parentType);
                     }
-                    const declaredType = getTypeOfPropertyOfType(parentType, text);
+                    const propType = getTypeOfPropertyOfType(parentType, text);
+                    const declaredType = propType && getApparentTypeForLocation(propType, declaration.name);
                     type = declaredType && getFlowTypeOfReference(declaration, declaredType) ||
                         isNumericLiteralName(text) && getIndexTypeOfType(parentType, IndexKind.Number) ||
                         getIndexTypeOfType(parentType, IndexKind.String);
@@ -12039,16 +12040,6 @@ namespace ts {
         }
 
         function getTypeWithFacts(type: Type, include: TypeFacts) {
-            if (type.flags & TypeFlags.IndexedAccess) {
-                // TODO (weswig): This is a substitute for a lazy negated type to remove the types indicated by the TypeFacts from the (potential) union the IndexedAccess refers to
-                //  - See discussion in https://github.com/Microsoft/TypeScript/pull/19275 for details, and test `strictNullNotNullIndexTypeShouldWork` for current behavior
-                const baseConstraint = getBaseConstraintOfType(type) || emptyObjectType;
-                const result = filterType(baseConstraint, t => (getTypeFacts(t) & include) !== 0);
-                if (result !== baseConstraint) {
-                    return result;
-                }
-                return type;
-            }
             return filterType(type, t => (getTypeFacts(t) & include) !== 0);
         }
 
@@ -13162,19 +13153,20 @@ namespace ts {
             const parent = node.parent;
             return parent.kind === SyntaxKind.PropertyAccessExpression ||
                 parent.kind === SyntaxKind.CallExpression && (<CallExpression>parent).expression === node ||
-                parent.kind === SyntaxKind.ElementAccessExpression && (<ElementAccessExpression>parent).expression === node;
+                parent.kind === SyntaxKind.ElementAccessExpression && (<ElementAccessExpression>parent).expression === node ||
+                parent.kind === SyntaxKind.NonNullExpression ||
+                parent.kind === SyntaxKind.BindingElement && (<BindingElement>parent).name === node && !!(<BindingElement>parent).initializer;
         }
 
         function typeHasNullableConstraint(type: Type) {
             return type.flags & TypeFlags.TypeVariable && maybeTypeOfKind(getBaseConstraintOfType(type) || emptyObjectType, TypeFlags.Nullable);
         }
 
-        function getDeclaredOrApparentType(symbol: Symbol, node: Node) {
+        function getApparentTypeForLocation(type: Type, node: Node) {
             // When a node is the left hand expression of a property access, element access, or call expression,
             // and the type of the node includes type variables with constraints that are nullable, we fetch the
             // apparent type of the node *before* performing control flow analysis such that narrowings apply to
             // the constraint type.
-            const type = getTypeOfSymbol(symbol);
             if (isApparentTypePosition(node) && forEachType(type, typeHasNullableConstraint)) {
                 return mapType(getWidenedType(type), getApparentType);
             }
@@ -13264,7 +13256,7 @@ namespace ts {
             checkCollisionWithCapturedNewTargetVariable(node, node);
             checkNestedBlockScopedBinding(node, symbol);
 
-            const type = getDeclaredOrApparentType(localOrExportSymbol, node);
+            const type = getApparentTypeForLocation(getTypeOfSymbol(localOrExportSymbol), node);
             const assignmentKind = getAssignmentTargetKind(node);
 
             if (assignmentKind) {
@@ -15816,7 +15808,7 @@ namespace ts {
                         return unknownType;
                     }
                 }
-                propType = getDeclaredOrApparentType(prop, node);
+                propType = getApparentTypeForLocation(getTypeOfSymbol(prop), node);
             }
             // Only compute control flow type if this is a property access expression that isn't an
             // assignment target, and the referenced property was declared as a variable, property,

tests/baselines/reference/definiteAssignmentOfDestructuredVariable.js

@@ -0,0 +1,28 @@
+//// [definiteAssignmentOfDestructuredVariable.ts]
+// https://github.com/Microsoft/TypeScript/issues/20994
+interface Options {
+    a?: number | object;
+    b: () => void;
+}
+
+class C<T extends Options> {
+    foo!: { [P in keyof T]: T[P] }
+
+    method() {
+        let { a, b } = this.foo;
+        !(a && b);
+        a;
+    }
+}
+
+//// [definiteAssignmentOfDestructuredVariable.js]
+var C = /** @class */ (function () {
+    function C() {
+    }
+    C.prototype.method = function () {
+        var _a = this.foo, a = _a.a, b = _a.b;
+        !(a && b);
+        a;
+    };
+    return C;
+}());

tests/baselines/reference/definiteAssignmentOfDestructuredVariable.symbols

@@ -0,0 +1,42 @@
+=== tests/cases/compiler/definiteAssignmentOfDestructuredVariable.ts ===
+// https://github.com/Microsoft/TypeScript/issues/20994
+interface Options {
+>Options : Symbol(Options, Decl(definiteAssignmentOfDestructuredVariable.ts, 0, 0))
+
+    a?: number | object;
+>a : Symbol(Options.a, Decl(definiteAssignmentOfDestructuredVariable.ts, 1, 19))
+
+    b: () => void;
+>b : Symbol(Options.b, Decl(definiteAssignmentOfDestructuredVariable.ts, 2, 24))
+}
+
+class C<T extends Options> {
+>C : Symbol(C, Decl(definiteAssignmentOfDestructuredVariable.ts, 4, 1))
+>T : Symbol(T, Decl(definiteAssignmentOfDestructuredVariable.ts, 6, 8))
+>Options : Symbol(Options, Decl(definiteAssignmentOfDestructuredVariable.ts, 0, 0))
+
+    foo!: { [P in keyof T]: T[P] }
+>foo : Symbol(C.foo, Decl(definiteAssignmentOfDestructuredVariable.ts, 6, 28))
+>P : Symbol(P, Decl(definiteAssignmentOfDestructuredVariable.ts, 7, 13))
+>T : Symbol(T, Decl(definiteAssignmentOfDestructuredVariable.ts, 6, 8))
+>T : Symbol(T, Decl(definiteAssignmentOfDestructuredVariable.ts, 6, 8))
+>P : Symbol(P, Decl(definiteAssignmentOfDestructuredVariable.ts, 7, 13))
+
+    method() {
+>method : Symbol(C.method, Decl(definiteAssignmentOfDestructuredVariable.ts, 7, 34))
+
+        let { a, b } = this.foo;
+>a : Symbol(a, Decl(definiteAssignmentOfDestructuredVariable.ts, 10, 13))
+>b : Symbol(b, Decl(definiteAssignmentOfDestructuredVariable.ts, 10, 16))
+>this.foo : Symbol(C.foo, Decl(definiteAssignmentOfDestructuredVariable.ts, 6, 28))
+>this : Symbol(C, Decl(definiteAssignmentOfDestructuredVariable.ts, 4, 1))
+>foo : Symbol(C.foo, Decl(definiteAssignmentOfDestructuredVariable.ts, 6, 28))
+
+        !(a && b);
+>a : Symbol(a, Decl(definiteAssignmentOfDestructuredVariable.ts, 10, 13))
+>b : Symbol(b, Decl(definiteAssignmentOfDestructuredVariable.ts, 10, 16))
+
+        a;
+>a : Symbol(a, Decl(definiteAssignmentOfDestructuredVariable.ts, 10, 13))
+    }
+}

tests/baselines/reference/definiteAssignmentOfDestructuredVariable.types

@@ -0,0 +1,45 @@
+=== tests/cases/compiler/definiteAssignmentOfDestructuredVariable.ts ===
+// https://github.com/Microsoft/TypeScript/issues/20994
+interface Options {
+>Options : Options
+
+    a?: number | object;
+>a : number | object | undefined
+
+    b: () => void;
+>b : () => void
+}
+
+class C<T extends Options> {
+>C : C<T>
+>T : T
+>Options : Options
+
+    foo!: { [P in keyof T]: T[P] }
+>foo : { [P in keyof T]: T[P]; }
+>P : P
+>T : T
+>T : T
+>P : P
+
+    method() {
+>method : () => void
+
+        let { a, b } = this.foo;
+>a : T["a"]
+>b : T["b"]
+>this.foo : { [P in keyof T]: T[P]; }
+>this : this
+>foo : { [P in keyof T]: T[P]; }
+
+        !(a && b);
+>!(a && b) : false
+>(a && b) : T["b"]
+>a && b : T["b"]
+>a : T["a"]
+>b : T["b"]
+
+        a;
+>a : T["a"]
+    }
+}

tests/baselines/reference/strictNullNotNullIndexTypeShouldWork.types

@@ -23,11 +23,11 @@ class Test<T extends A> {
         this.attrs.params!.name;
 >this.attrs.params!.name : string
 >this.attrs.params! : { name: string; }
->this.attrs.params : T["params"]
+>this.attrs.params : { name: string; } | undefined
 >this.attrs : Readonly<T>
 >this : this
 >attrs : Readonly<T>
->params : T["params"]
+>params : { name: string; } | undefined
 >name : string
     }
 }
@@ -80,10 +80,10 @@ class Test2<T extends A> {
 
         return this.attrs.params!; // Return type should maintain relationship with `T` after being not-null-asserted, ideally
 >this.attrs.params! : { name: string; }
->this.attrs.params : T["params"]
+>this.attrs.params : { name: string; } | undefined
 >this.attrs : Readonly<T>
 >this : this
 >attrs : Readonly<T>
->params : T["params"]
+>params : { name: string; } | undefined
     }
 }

tests/cases/compiler/definiteAssignmentOfDestructuredVariable.ts

@@ -0,0 +1,16 @@
+// @strictNullChecks: true
+// https://github.com/Microsoft/TypeScript/issues/20994
+interface Options {
+    a?: number | object;
+    b: () => void;
+}
+
+class C<T extends Options> {
+    foo!: { [P in keyof T]: T[P] }
+
+    method() {
+        let { a, b } = this.foo;
+        !(a && b);
+        a;
+    }
+}